Acid anhydrides, in particular succinic anhydride, are valuable reactive intermediates commonly used in a variety of applications. For example, acid anhydrides are used in copolymers to produce biodegradable polyesters. Additionally, acid anhydrides are useful intermediates in organic synthesis because they are easily ring opened to form diacids or other derivatives. Succinic anhydride is particularly useful as a precursor to 4 carbon commodity chemicals such as tetrahydrofuran, gamma butyrolactone and 1,4-butanediol.
Previous production methods for acid anhydrides, including succinic anhydride, included dehydration of corresponding acids or hydrogenation of maleic anhydride. Additional production methods include catalyzed carbonylation of alkynes, alkenoic acids and lactones. Many of the methods suffered from low yield, production of many byproducts or lacked generality. Novel methods using more cost effective starting materials are sought.
U.S. Pat. No. 6,852,865 discloses a class of well-defined bimetallic catalysts of the general type [Lewis acid]+[M(CO)x]− for the ring-expanding carbonylation of strained heterocycles. Related catalysts can carbonylate the resulting β-lactones to succinic anhydrides in high yields while preserving stereochemical purity. Given the many syntheses of enantiomerically pure epoxides and the recent advances in epoxide carbonylation to β-lactones, subsequent carbonylation of these β-lactones constitutes a versatile two-step method for the stereoselective synthesis of succinic anhydrides. (Scheme 1).
